1. Field of the Invention
This invention pertains to the field of forming splined surfaces particularly on sheet metal components and more particularly to producing splines having shallow pressure angles produced by successive passes through forming dies.
2. Description of the Prior Art
Currently automatic transmissions have heavy cast or forged clutch and brake cylinders formed with splines on their outer surfaces. The splines permit axial movement in a guided relationship upon being pressurized by the hydraulic system of the transmission. The clutch and brake cylinders have walls that are thick and strong enough so that internal and external splines can be machined on their cylindrical surfaces. Lighter weight clutch and brake cylinders for an automatic transmission could be made if the splines could be formed by cold working processes such as by drawing the spline contour on sheet metal cups. Accurately controlled spline contours must be produced by the process for use in an automatic transmission, however.
It is a requirement, particularly in automatic transmission applications of a sheet metal splined cylinder, that the pressure angle be kept low and the corner radii of the splines be fairly tight. In this way, reliable positive engagement between internal and external meshing splines can be assured. If the pressure angle is too shallow, the height of the splines must be made correspondingly greater in order to maintain the contact pressures produced by the torque being transmitted between the splines at an acceptable level. This is a particularly important problem when the splined surfaces are formed on sheet metal whose dimensional stability under the radial loads produced by the torque is considerably less than that of the conventional cast or forged clutch and brake cylinders.